The fabrication and electrical properties of modulated stacked capacitor for advanced DRAM applications

A capacitor structure, called the modulated stacked (MOST) capacitor, has been developed to increase the DRAM cell capacitance using surface modulation technology. The hemispherical-shaped polysilicon deposited on top of a thick polysilicon storage electrode is used as a mask to selectively form a deep groove in the electrode, hence significantly increasing the surface area. With this structure, the surface area of the storage electrode can be increased by as much as 8 times that of an ordinary stacked capacitor (STC) which takes the same chip area. Experimental results show that electrical properties such as leakage current, breakdown voltage, and TDDB are comparable to those of a conventional stacked capacitor.>